Name: photobleaching enables super-resolution imaging of the ftsz ring in the cyanobacterium prochlorococcus
Uploaded: 2018-11-06T15:00:00
Description: Watch this Scientific Journal Video about Photobleaching Enables Super-resolution Imaging of the FtsZ Ring in the Cyanobacterium Prochlorococcus at JoVE.com

The authors thank Daiying Xu for her technical assistance and comments on the manuscript. This study is supported by grants from the National Natural Science Foundation of China (Project number 41476147) and the Research Grants Council of the Hong Kong Special Administrative Region, China (project numbers 689813 and 16103414).

1. Sample Preparation and Fixation
<ol>
	<li>Inoculate 1 mL of axenic Prochlorococcus MED4 to 5 mL of the seawater-based Pro99 medium12. Grow Prochlorococcus cultures at 23 &#176;C under the light with an intensity of 35 &#181;mol photons/m2s. Five days later, collect 1 mL of culture into a 1.5-mL tube. 
	NOTE: Five days after the inoculation, Prochlorococcus MED4 will reach the late log phase, with approximately 108 cell/mL, which is appropr...

<ol>
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In this protocol, we described a procedure to significantly reduce the autofluorescence of the cyanobacterium Prochlorococcus (Figure 3C) and, then, immunostain the proteins in the cells, which enabled us to utilize STORM to study the 3-D FtsZ ring morphologies in Prochlorococcus (Figure 4). This protocol might be adopted for super-resolution imaging in other photosynthetic organisms.
Previous studies on photosynthet...

Super-resolution microscopies can break the diffraction limit of light and provide images within sub-diffraction resolutions (&#60; 200 nm). They have been widely used in many organisms to study protein localization and subcellular structures. Major super-resolution microscopy methods include structured illumination microscopy (SIM), stimulated emission depletion microscopy (STED), STORM, and photoactivated localization microscopy (PALM). The mechanisms and applications of these super-resolution microscopes have been reviewed elsewhere1,2.
STORM can achieve a resolution as high as 10 nm by spatial separation3,4. For STORM, only one molecule within a diffraction-limited region is activated (&#34;on&#34;) and the rest of the molecules are kept inactivated (&#34;off&#34;). By an accumulation of rapid switch-on and -off of single molecules, a &#34;diffraction-unlimited&#34; image can be generated3. Meanwhile, many kinds of organic dyes and fluorescent proteins are applicable in STORM, allowing an easy upgrade from regular fluorescence microscopy to high-resolution microscopy5,6.
STORM has not been widely applied in photosynthetic cells, such as cyanobacteria, algae, and plant cells with chloroplasts7,8, which is due to the fact that STORM requires high laser intensity to drive photoswitching. The high-intensity laser unfavorably excites strong autofluorescence background in photosynthetic cells and interferes with the single-molecule localization in STORM imaging. In order to use STORM to investigate the subcellular structures or protein interactions in photosynthetic cells, we developed a photobleaching protocol to quench the background autofluorescence signals9. In a routine immunofluorescent staining procedure, specimens are exposed to white light of a high intensity during the blocking step, which lowers the autofluorescence of photosynthetic cells to meet the requirements for STORM. Thus, this protocol makes it feasible to investigate pigmented organisms with STORM.
Here, we describe the protocol to use STORM to image the FtsZ ring organization in the unicellular picocyanobacterium Prochlorococcus. FtsZ is a highly conserved tubulin-like cytoskeletal protein which polymerizes to form a ring structure (the Z ring) around the circumference of a cell10 and is essential for the cell division11. Preserved Prochlorococcus cells are first photobleached to reduce the autofluorescent background and immunostained with a primary anti-FtsZ antibody, and then a secondary anti-Rabbit IgG (H+L) antibody is conjugated with a fluorophore (e.g., Alexa Fluor 750). Eventually, STORM is used to observe the detailed FtsZ ring organizations in Prochlorococcus during different cell cycle stages.

<table>
	<tbody>
		<tr>
			<td>Polystyrene particles</td>
			<td>Spherotech</td>
			<td>PP-20-10</td>
			<td>2.0-2.4 &#181;m</td>
		</tr>
		<tr>
			<td>Coverslip</td>
			<td>Marienfeld</td>
			<td>0111580</td>
			<td>18 mm &#8709;, Thickness No. 1</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Scharlau</td>
			<td>ET00021000</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly-L-lysine hydrobromide</td>
			<td>Sigma-Aldrich</td>
			<td>P9155</td>
			<td>mol wt 70,000-150,000</td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>158127</td>
			<td></td>
		</tr>
		<tr>
			<td>Glutaraldehyde solution, 50%</td>
			<td>Sigma-Aldrich</td>
			<td>340855</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Sigma</td>
			<td>P3813</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma</td>
			<td>T8787</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA Disodium Salt, 2-hydrate</td>
			<td>Gold biotechnology</td>
			<td>E-210-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Trizma base</td>
			<td>Sigma</td>
			<td>T1503</td>
			<td></td>
		</tr>
		<tr>
			<td>Lysozyme</td>
			<td>Sigma</td>
			<td>L6876</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat serum</td>
			<td>Sigma</td>
			<td>G9023</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-Anabaena FtsZ antibody</td>
			<td>Agrisera</td>
			<td>AS07217</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Rabbit IgG (H+L) Cross-Adsorbed Secondary Antibody</td>
			<td>Life Technologies</td>
			<td>A-21039</td>
			<td>conjugated with Alexa Fluor 750</td>
		</tr>
		<tr>
			<td>D-Glucose Anhydrous</td>
			<td>Fisher Scientific</td>
			<td>D16-1</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Ascorbic Acid</td>
			<td>Sigma-Aldrich</td>
			<td>A5960</td>
			<td></td>
		</tr>
		<tr>
			<td>Methyl Viologen</td>
			<td>Sigma-Aldrich</td>
			<td>856177</td>
			<td></td>
		</tr>
		<tr>
			<td>Cyclooctatetraene</td>
			<td>Sigma-Aldrich</td>
			<td>138924</td>
			<td></td>
		</tr>
		<tr>
			<td>tris(2-carboxyethyl)phosphine (TCEP)</td>
			<td>Sigma-Aldrich</td>
			<td>646547</td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose Oxidase</td>
			<td>Sigma-Aldrich</td>
			<td>G2133</td>
			<td></td>
		</tr>
		<tr>
			<td>Catalase</td>
			<td>Sigma-Aldrich</td>
			<td>C9322</td>
			<td></td>
		</tr>
		<tr>
			<td>XD-300 Xenon light source</td>
			<td></td>
			<td></td>
			<td>250 W</td>
		</tr>
		<tr>
			<td>STORM microscope</td>
			<td>NBI</td>
			<td>SRiS microscope</td>
			<td></td>
		</tr>
		<tr>
			<td>Rohdea</td>
			<td>NBI</td>
			<td>SRiS 3.0</td>
			<td>software for imaging acquisition</td>
		</tr>
		<tr>
			<td>Luna</td>
			<td>NBI</td>
			<td>SRiS 3.0</td>
			<td>software for drifting correction</td>
		</tr>
		<tr>
			<td>QuickPALM</td>
			<td></td>
			<td></td>
			<td>https://code.google.com/archive/p/quickpalm/wikis</td>
		</tr>
		<tr>
			<td>3D Viewer</td>
			<td></td>
			<td></td>
			<td>http://132.187.25.13/ij3d/?page=Home&#38;category=Home</td>
		</tr>
	</tbody>
</table>

photobleaching enables super-resolution imaging of the ftsz ring in the cyanobacterium prochlorococcus

Super-resolution microscopy has been widely used to study protein interactions and subcellular structures in many organisms. In photosynthetic organisms, however, the lateral resolution of super-resolution imaging is only ~100 nm. The low resolution is mainly due to the high autofluorescence background of photosynthetic cells caused by high-intensity lasers that are required for super-resolution imaging, such as stochastic optical reconstruction microscopy (STORM). Here, we describe a photobleaching-assisted STORM method which was developed recently for imaging the marine picocyanobacterium Prochlorococcus. After photobleaching, the autofluorescence of Prochlorococcus is effectively reduced so that STORM can be performed with a lateral resolution of ~10 nm. Using this method, we acquire the in vivo three-dimensional (3-D) organization of the FtsZ protein and characterize four different FtsZ ring morphologies during the cell cycle of Prochlorococcus. The method we describe here might be adopted for the super-resolution imaging of other photosynthetic organisms.

STORM achieves super-resolution imaging by activating individual photoswitchable fluorophores stochastically. The location of every fluorophore is recorded and a super-resolution image is then constructed based on these locations4. Therefore, the precision of the fluorophore location is important for the super-resolution image reconstruction. The absorption spectra of Prochlorococcus peak at 447 nm and 680 nm,and Prochlorococcus has a minimum abso...

Watch this Scientific Journal Video about Photobleaching Enables Super-resolution Imaging of the FtsZ Ring in the Cyanobacterium Prochlorococcus at JoVE.com

Photobleaching Enables Super-resolution Imaging of the FtsZ Ring in the Cyanobacterium Prochlorococcus

Here we describe a photobleaching method to reduce the autofluorescence of cyanobacteria. After photobleaching, stochastic optical reconstruction microscopy is used to obtain three-dimensional super-resolution images of the cyanobacterial FtsZ ring.

Photobleaching Enables Super-resolution Imaging of the FtsZ Ring in the Cyanobacterium Prochlorococcus

Super-resolution microscopy has been widely used to study protein interactions and subcellular structures in many organisms. In photosynthetic organisms, ...

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